INTRODUCTION: The purpose of this investigation was to identify factors associated with Air Force aviators delaying ejection during in-flight emergencies.METHODS: The investigator reviewed all reports within the Air Force Safety Automated System describing mishaps that resulted in the destruction of Air Force ejection-seat equipped aircraft between 1993 and 2013. Crewmembers were classified as either timely or delayed ejectors based on altitude at onset of emergency, altitude at ejection, and a determination regarding whether or not the aircraft was controlled during the mishap sequence. Univariate analysis and multivariate logistic regression were used to explore the association between delayed ejection and multiple potential risk factors.RESULTS: In total, 366 crewmembers were involved in in-flight emergencies in ejection-seat-equipped aircraft that resulted in the loss of the aircraft; 201 (54.9%) of these crewmembers delayed ejection until their aircraft had descended below recommended minimum ejection altitudes. Multivariate analysis indicated that independent risk factors for delayed ejection included increased crewmember flight hours and a mechanical or human-factors related cause of the emergency versus bird strike or midair collision.DISCUSSION: This investigation provided quantitative assessments of factors associated with aviators delaying ejection during in-flight emergencies. Increased odds of delay among crewmembers with greater than 1500 total flight hours suggests that complacency and overconfidence may adversely influence the ejection decision to at least as great a degree as inexperience. Increased odds of delay during mechanical and human factors mishaps confirms previously reported hypotheses and reaffirms the importance of targeting these areas to reduce aviator injuries and fatalities.Miles JE. Factors associated with delayed ejection in mishaps between 1993 and 2013. Aerosp Med Hum Perform. 2015; 86(9):774–781.

INTRODUCTION: It has been demonstrated that the cerebrovascular response to hypoxia is blunted following 10 d of intermittent hypoxia (IH) in healthy humans. The purpose of this study was to test the hypothesis that IH reduces the cerebrovascular response to CO₂.METHODS: Healthy male subjects (N = 8; 25 ± 2 yr) were exposed to 10 consecutive days of IH (12% O₂ for 5 min followed by 5 min of normoxia for 1 h/d). The cerebrovascular response to CO₂ was assessed prior to (PRE-IH) and following (POST-IH) the IH paradigm with transcranial Doppler ultrasound.RESULTS: There was no change in eupnic measures during or following the IH paradigm; however, the ventilatory response to IH increased by the last exposure (3.0 ± 2.8 L · min⁻¹). Cerebral blood flow velocity decreased and increased with hypocapnia and hypercapnia, respectively, but cerebrovascular sensitivity to CO₂ remained unchanged with IH (PRE-IH: 2.58 ± 0.50%/mmHg; POST-IH: 2.59 ± 0.74%/mmHg).DISCUSSION: Our data indicates that 10 d of IH in healthy humans does not alter the cerebrovascular response to CO₂. Redundancy of cerebrovascular regulation mechanisms to CO₂ may work to counteract IH-induced dysregulation and protect cerebral tissue.Querido JS, Welch JF, Ayas NT, Sheel AW. Cerebrovascular response to CO₂ following 10 days of intermittent hypoxia in humans. Aerosp Med Hum Perform. 2015; 86(9):782–786.

BACKGROUND: In field studies, motion sickness is more common among women than among men. In laboratory research sex differences have been smaller, or absent. However, laboratory research on sex differences in motion sickness has employed exclusively rotational motion stimuli. We evaluated sex differences when motion sickness was induced using linear visual oscillation.METHOD: Standing subjects were exposed to linear visual oscillation along the line of sight. We separately assessed the incidence of motion sickness and the severity of symptoms that are associated with motion sickness.RESULTS: The incidence of motion sickness was 38% among women, but only 9% among men. Among subjects who stated that they were motion sick, the severity of symptoms did not differ between women and men.CONCLUSIONS: Motion sickness induced using linear visual oscillatory stimuli exhibited sex differences greater than those that have been reported in field studies. Sex differences in motion sickness may vary as a function of the type of motion stimulation (linear versus angular).Koslucher F, Haaland E, Malsch A, Webeler J, Stoffregen TA. Sex differences in the incidence of motion sickness induced by linear visual oscillation. Aerosp Med Hum Perform. 2015; 86(9):787–793.

INTRODUCTION: Although the induction of vection (perception of illusory self-motion) has been studied for some decades, the effect of ground surface properties on vection remains to be assessed quantitatively. This study will be helpful for designing helicopter or airplane flight simulation, because pilots often perceive optic flow on the ground surface and perceive self-motion from such flows.METHOD: Vection stimuli of variable position, size, and optic flow speed were presented in a trapezoidal area on a ground surface. Body sway was also measured.RESULTS: Substantial vection was induced by stimuli on a ground surface. Increases in stimulus speed and size were each associated with stronger vection (e.g., the subjective strength increased by 50% as the speed increased from 0.375 m · s⁻¹ to 1.5 m · s⁻¹). When the stimulus occupied a more distant section of the visual field, vection was more efficiently induced than when the nearer section was occupied (e.g., the subjective strength decreased by 50% when the nearer half section of optical flow was removed). These properties of vection were similar to vection induced by upright vertical stimuli. Speed, size, and position of vection stimuli modified both length and direction of body sway significantly. Vection and body sway showed some correlations (e.g., r = 0.55).CONCLUSION: Stimuli on ground surfaces can induce substantial vection and vection strength can be modified by the stimulus properties of the ground surfaces.Tamada Y, Seno T. Roles of size, position, and speed of stimulus in vection with stimuli projected on a ground surface. Aerosp Med Hum Perform. 2015; 86(9):794–802.

BACKGROUND: Hind limb unloading (HU) is one of the ground-based models of simulated microgravity. As bacterial and viral infections could affect the immune system, the immunologic effect of HU should be studied in a specific-pathogen-free (SPF) laboratory. However, a review of the literature did not reveal any studies on the immunologic effects of prolonged HU in a murine model of allergic disease. Accordingly, the present study was undertaken to evaluate the effect of HU in a murine model of allergic asthma in a SPF laboratory.METHODS: Twenty BALB/c mice were allocated equally to Group A (control group), Group B (HU group), Group C (allergic group), or Group D (allergic + HU group). Weight gains, serum total and ovalbumin (OVA)-specific IgE, titers of IL-1, IL-5, IL-10, and IFN-γ in bronchoalveolar lavage (BAL) fluid, and histopathologic findings of the lungs were compared.RESULTS: After 2 wk of HU, Group D showed significantly more weight loss (−2.0 ± 0.2 g) than Group C (−1.1 ± 0.4 g). Groups B and D showed significant increases in serum OVA-specific IgE as compared with Groups A and C. Group D had significantly lower titers of IL-5 (Group C: 53.0 ± 15.2 pg · ml⁻¹, Group D: 21.9 ± 13.9 pg · ml⁻¹), IL-10 (Group C: 430.8 ± 138.3 pg · ml⁻¹, Group D: 217.6 ± 51.2 pg · ml⁻¹), and IFN-γ (Group C: 104.3 ± 37.5 pg · ml⁻¹, Group D: 36.7 ± 12.8 pg · ml⁻¹) in BAL fluid than Group C. Peri-bronchiolar and pulmonary infiltrations of inflammatory cells were significantly greater in Group D than in Group C.CONCLUSIONS: Prolonged HU may cause significant weight loss and aggravate disease courses.Jang TY, Heo M-J, Jung A-Y, Kim YH. Prolonged anti-orthostatic hind limb unloading and murine allergic asthma. Aerosp Med Hum Perform. 2015; 86(9):803–807.

INTRODUCTION: Radio communication remains important for the delivery of safety-critical information in military aviation. Pilots are exposed to high noise levels. Noise attenuation provided by certain helmets is not sufficient, and resulting noise exposure can deteriorate operational effectiveness and flight safety. A need for hearing protection that enables efficient communication is obvious, especially for fighter and helicopter pilots. One possible solution for this issue is molded communication earplugs (m-CEP). Data about the advantages and disadvantages of m-CEPs are limited.METHODS: To determine the usage rates, advantages, disadvantages and pilot opinions about m-CEPs, an anonymous survey study including 31 questions was conducted in fighter, fighter trainer, helicopter, and transport aircraft units of the Finnish Defense Forces.RESULTS: Of the pilots who responded, 136 (93%) had used or tried m-CEPs and 90 (62%) were currently using them. There are many benefits to m-CEPs: they seem to enhance experienced speech intelligibility, since 85% of the pilots who had experience about them reported improved speech intelligibility under difficult hearing conditions, and 93% would recommend them to other pilots. It seems m-CEPs provide equal benefits to pilots with and without current hearing problems. They were also considered better than previously used hearing protectors. Still, problems were common: 82% of the pilots reported m-CEP related drawbacks, of which technical problems and discomfort issues were the most prevalent.DISCUSSION: Most military pilots hold a positive opinion on m-CEPs and are willing to recommend their use. Technical problems and discomfort issues are, however, relatively common.Lahtinen TMM, Leino TK. Molded communication earplugs in military aviation. Aerosp Med Hum Perform. 2015;86(9):808–814.

INTRODUCTION: Warfighters involved in mounted operations often experience prolonged periods of tissue loading, leading to injury. Determining how anatomical structures are affected during loading aids in the prevention and treatment of injury. The purpose of this study was to develop a magnetic resonance imaging (MRI) compatible seat system that simulates a UH-60 Blackhawk in-flight sitting posture.METHODS: Eight men were scanned with a 3.0 Tesla MRI. Scans were collected with and without 6.38 psi of pressure applied to the buttocks via two air bladders and an MRI-compatible robot controller system.RESULTS: Scans revealed that 6.38 psi of pressure applied to the buttocks significantly decreases total soft-tissue thickness beneath the left and right ischial tuberosities by 3.6 and 3.8 mm, respectively.DISCUSSION: At operational load bearing pressures seen in the UH-60, the soft tissue structures of the buttocks are compressed. These findings aid in our understanding of the etiology of repetitive trauma disorders in aircrew due to prolonged sitting. This study serves as the foundation for future work examining the anatomical changes associated with prolonged restricted sitting and other operational activities. A better understanding of the anatomical characteristics associated with mounted operations is invaluable to the prevention and treatment of injuries reported by warfighters and civilian populations.Games KE, Kollock RO, Windham J, Fischer GS, Sefton JM. Tissue changes during operational load bearing in UH-60 aircrew using magnetic resonance imaging. Aerosp Med Hum Perform. 2015; 86(9):815–818.

INTRODUCTION: A space mission’s crewmembers are the most important group of people involved and, thus, their emotions and interpersonal interactions have gained significant attention. Because crewmembers are confined in an isolated environment, the aim of this study was to identify possible changes in the emotional states, group dynamics, displacement, and leadership of crewmembers during an 80-d isolation period.METHODS: The experiment was conducted in an analogue space station referred to as Lunar Palace 1 at Beihang University. In our experiment, all of the crewmembers completed a Profile of Mood States (POMS) questionnaire every week and two group climate scales questionnaires every 2 wk; specifically, a group environment scale and a work environment scale.RESULTS: There was no third-quarter phenomenon observed in Lunar Palace 1. However, fluctuations in the fatigue and autonomy subscales were observed. Significant displacement effects were observed when Group 3 was in the analogue. Leader support was positively correlated with the cohesion, expressiveness, and involvement of Group 3. However, leader control was not.DISCUSSION: The results suggest that time effects, displacement, and leadership roles can influence mood states and cohesion in isolated crew. These findings from Lunar Palace 1 are in agreement with those obtained from Mir and the International Space Station (ISS).Wang Y, Wu R. Time effects, displacement, and leadership roles on a lunar space station analogue. Aerosp Med Hum Perform. 2015; 86(9):819–823.

BACKGROUND: Using concepts from evidence-based medicine, systems theory, and risk assessment, a standardized model was developed to accept or reject medications for use in flight. The model calculates the risk scores of medications, which can then be compared to an organization’s acceptable risk tolerance.METHODS: Risk scores for each medication were established by summing the products of incidence rates and severity scores for all published side effects. The incidence of each side effect was obtained in an evidence-based manner and each assigned a severity multiplier. Using statistical analysis of the calculated risk scores of approved medications, an acceptance control chart was generated.RESULTS: Range of calculated risk scores of historically approved medications was 10–9140. Six Sigma Acceptance Control Line was calculated at 1.5 SDs above the mean and was 9822. Risk score range of medications generally felt unsafe was 27,010–41,294. Risk score range of medications under consideration for approval was 986–6863.DISCUSSION: This novel approach to medication approval is the first in aerospace medicine to attempt to combine evidence-based medicine, risk analysis, and control charts to standardize and streamline the medication approval process within an organization. The model was validated by testing against medications generally accepted to be unsafe for use in flight. These medications fell several deviations above the control line. Other medications not yet authorized fall well below the acceptance line and could be considered for approval.Prudhomme MB, Ropp LG, Sauer SW, LaVan JT. Aeromedical risk assessment of pharmaceuticals using evidence-based medicine. Aerosp Med Hum Perform. 2015; 86(9):824–829.

INTRODUCTION: The first space-based fused deposition modeling (FDM) 3D printer is powered by solar photovoltaics. This study seeks to demonstrate the feasibility of using solar energy to power a FDM 3D printer to manufacture medical resources at the Mars Desert Research Station and to design an ultra-portable solar-powered 3D printer for off-grid environments.METHODS: Six solar panels in a 3 × 2 configuration, a voltage regulator/capacitor improvised from a power adapter, and two 12V batteries in series were connected to power a FDM 3D printer. Three designs were printed onsite and evaluated by experts post analogue mission. A solar-powered 3D printer composed of off-the-shelf components was designed to be transported in airline carry-on luggage.RESULTS: During the analogue mission, the solar-powered printer could only be operated for < 1 h/d, but was able to fabricate a functional dental tool, scalpel handle, and customized mallet splint over 2 d. Post analogue mission, an ultra-portable plug-and-play solar-powered 3D printer was designed that could print an estimated 16 dental tools or 8 mallet finger splints or 7 scalpel handles on one fully charged 12V 150Wh battery with a 110V AC converter.CONCLUSION: It is feasible to use solar energy to power a 3D printer to manufacture functional and personalized medical resources at a Mars analogue research station. Based on these findings, a solar-powered suitcase 3D printing system containing solar panels, 12V battery with charge controller and AC inverter, and back-up solar charge controller and inverter was designed for transport to and use in off-grid communities.Wong JY. Ultra-portable solar-powered 3D printers for onsite manufacturing of medical resources. Aerosp Med Hum Perform. 2015; 86(9):830–834.

BACKGROUND: Debate regarding the merits of screening pilots for sleep apnea has been stimulated by recently issued guidance from the Federal Aviation Administration. It has long been appreciated that sleep apnea results in poor quality sleep, and that poor quality sleep is associated with daytime fatigue and decrements in performance. However, the relationship between sleep apnea and poor performance, including risk for accidents is not as well understood. Good quality data are available for commercial truck drivers and have helped influence transportation policy, but there is a lack of pilot specific data. The purpose of this article is to review the basic epidemiology, pathophysiology, and treatment of sleep apnea, including major risk factors for apnea, such as body mass index (BMI), and to look at what is known about the impact of sleep apnea on performance in transportation related occupations. While pilot specific data may be lacking, good quality data for commercial truckers are available and can be used to formulate rational public policy with the goal of improving aviation safety. This article was reviewed by the Council of the Aerospace Medical Association and approved as a position paper of the Association.Ruskin KJ, Caldwell JA, Caldwell JL, Boudreau EA. Screening for sleep apnea in morbidly obese pilots. Aerosp Med Hum Perform. 2015; 86(9):835–841.

Duffy TD. You’re the flight surgeon: acute low back pain. Aerosp Med Hum Perform. 2015; 86(9):842–845.

Hatfield JM. You’re the flight surgeon: optic neuritis. Aerosp Med Hum Perform. 2015; 86(9):845–848.